Hoffman, 40, spent much of his 20-year Navy career on submarines as a cryptologic technician. After he went on a three-week trip to Eastern Europe in 2011, the FBI sent Hoffman a medal and letter in 2012 purporting to be from Russian intelligence officers asking him to provide “technical expertise,” Assistant U.S. Attorney Alan Salsbury said during opening statements.

Hoffman made three drops in all, including one in which he provided his handlers with information about how to track American submarines. Hoffman communicated via email and in a series of dead drops at First Landing State Park in Virginia Beach with an FBI agent using the pseudonym “Vladimir.” The two signaled each other when items were ready to be picked up by sticking electrical tape to a map at the park.

After the third drop, in which Hoffman also gave the handler classified information as to how the U.S. tracks foreign warships, Hoffman approached the FBI in Norfolk and gave agents a diary he’d been keeping of his “mission” and other evidence, including some tape his handlers had touched in the hopes the FBI could get a fingerprint from it.

He claimed he had tried to lure in the spies so they could be caught.

“The information was passed to aid the United States. … He wanted to lure them in,” said Assistant Federal Public Defender Keith Kimball, one of two attorneys representing Hoffman. “He was acting, perhaps foolishly, but not criminally.”

Media outlets report the trial is expected to last into next week.

The crime carries a possible death sentence, but federal prosecutors say they will not pursue that penalty.